Aspen Plus & Dynamic Workshop (Step by Step)

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Aspen Plus & Aspen

Dynamic Workshop

Driven by Innovation

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Presentation Outline

• Part 1: Introduction to Aspen Plus

• Introduction to AspenONE

• Introduction to Flowsheet simulation

• What is Aspen Plus?

• What Aspen Plus can do?

• Aspen Plus extension- Aspen Dynamic

• Steady state and Dynamic model dilemma

• How Aspen can help me with my research?

• Part 2: Before starting with Aspen Plus

• Process “know how” • Process Analysis

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D. Muhammad & AspenTech, 2013

Presentation Outline

• Part 3: Getting Started with Aspen Plus

• Distillation column design

• Aspen Analysis  Binary Analysis  Azeotrope Analysis  Design Specs  Sensitivity Analysis  Optimization

• Part 4: From Aspen Plus to Aspen Dynamic • Part 5: Aspen Dynamic with Matlab

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PART 1:

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Introduction to AspenONE

• Developed by AspenTech Inc.

• Integrated simulation software to implement best practices for:

Process design and modelling

Optimization engineering

Production management

Supply chain operation

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General Simulation Problem

What is the composition of stream PRODUCT?

To solve this problem, we need:

• Material balances • Energy balances REACTOR FEED RECYCLE REAC-OUT COOL COOL-OUT SEP PRODUCT

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Flowsheet Simulation

What is flowsheet simulation?

Use of a computer program to quantitatively model the characteristic equations of a chemical process

Uses underlying physical relationships

•Mass and energy balance

•Equilibrium relationships

•Rate correlations (reaction and mass/heat transfer)

Predicts

•Stream flowrate, compositions, and properties

•Operating conditions

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Approaches to Flowsheet Simulation

Sequential Modular

•Each unit operation block is solved in a certain sequence

•Aspen Plus is a sequential modular simulation program

Equation Oriented

•All equations are solved simultaneously

•Aspen Custom Modeler (formerly SPEEDUP) is an equation oriented simulation program

Combination

•Aspen Dynamics (formerly DynaPLUS) uses the Aspen Plus sequential modular approach to initialize the steady state simulation and the Aspen Custom Modeler (formerly SPEEDUP) equation oriented approach to solve the dynamic simulation

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Sequential-Modular

Approach

Equation Oriented

Approach

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Advantage of Simulation

Reduces plant design time

•Allows designer to quickly test various plant configurations

Helps improve current process

•Answers “what if” questions

•Determines optimal process conditions within given constraints

•Assists in locating the constraining parts of a process (debottlenecking)

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Good Flowsheeting Practice

• Build large flowsheets a few blocks at a time.

This facilitates troubleshooting if errors occur.

• Ensure flowsheet inputs are reasonable.

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What is Aspen Plus?

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Aspen Plus Inputs

Aspen Plus

Process

Simulation

Model Inputs

Process Flowsheet Design Specify Chemical Components Choose Thermodynamic Models Specify Feed Conditions Specify Operating Conditions

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What Aspen Plus can do?

• Flowsheet (default): process simulation (SA and optimization) • Data Regression: fitting data to existing models in Aspen

• Property Display: show properties of a components in Aspen Plus’s database

• Property Analysis: estimating physical and thermodynamic properties • Assay Data Analysis: analyze assay data (petroleum application)

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Aspen Plus Extension: Aspen Dynamic

• Dynamic modeling tool for plant operations and process design • Enables users to study and understand the dynamics of real plant operations

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Adding Dynamic Data

Data is required to calculate the following:

• Vessel geometry (required for vessel volume)

• Vessel initial filling (used for starting liquid holdup) • Process heat-transfer method

• Equipment heat transfer options

 Equipment heat capacity

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Steady state vs. Dynamic dilemma

Steady state

• All properties are steady

(not changing over time).

• Can be used to study

different steady state

conditions for a specific

range of properties either at

operating conditions or

off-design conditions.

Dynamic

• Ability to model the time

varying behaviour of a

system (changing over time)

• Used to analyse the

dynamic behaviour

(response) of complex

systems.

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Advantages of Steady State Simulation

• Immediate answers to system condition variation • Determine results at specific conditions

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Advantages of Dynamic Simulation

• Determine behaviour of plant/system over complete operating range: start up, shut down, accident scenarios, transition between different states and disturbances occurrence (what if –behaviour)

• Can identify in advance if the operating problems occurred

• Facilitate the design for control and optimization of process components to ensure optimum system behaviour, even during off design and transient behaviour

• Design and commission control systems using simulations and just fine tune during actual installations

• Dynamic integrated simulations can help to identify bottlenecks, inefficiencies and safety risks that are not identifiable with steady-state or segregated simulation

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Application for SS and Dynamic Simulation

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How Aspen can help me with my research?

• Another option for first principle model (FPM)

• Simulation and validation of complex chemical process •Sensitivity analysis and optimization study of process • Study nonlinearity and multiplicity behavior in process

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PART 2:

BEFORE STARTING WITH

ASPEN PLUS

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Process “know how”

• Aspen Plus is not a magic box

• All the process inputs (e.g. sizing and process condition) must based on facts or heuristic justification

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Process Analysis

• Used to generate simple property diagrams to validate physical property models and data

• Understand the behavior of the process • Diagram Types:

Pure component, e.g. Vapor pressure vs. temperature

Binary, e.g. TXY, PXY

Ternary residue maps

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Aspen Property Method

• A collection of thermodynamic models and methods used to calculate physical properties.

• Choice of model types depends on degree of non-ideal behavior and operating conditions

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Case Study - Acetone Recovery

• Correct choice of physical property models and accurate physical property parameters are essential for obtaining accurate simulation results.

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Ideal vs. Non-Ideal Behavior

What do we mean by ideal behavior?

•Ideal Gas law and Raoult’s law

Which systems behave as ideal?

•Non-polar components of similar size and shape

What controls degree of non-ideality?

•Molecular interactions

e.g. Polarity, size and shape of the molecules

How can we study the degree of non-ideality of a system?

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Common Property Methods

Equation of State Property Methods

• PENG-ROB

• RK-SOAVE

Activity Coefficient Property Methods

• NRTL

• UNIFAC

• UNIQUAC

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Choosing a Property Method - Review

References:

Aspen Plus User Guide, Chapter 7, Physical

Property Methods, gives similar, more detailed guidelines for choosing a property Method.

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PART 3:

GETTING STARTED WITH

ASPEN PLUS

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Run ID Tool Bar Title Bar Menu Bar Select Mode button Model Library Model Menu Tabs _Process Flowsheet Window Next Button Status Area

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Case Study

Design a distillation process to separate isobutane and propane so that the impurity target in distillate is 2 wt% and in bottom is 1 wt%

Feed: Propane (40%) Isobutane (60%) Flowrate: 100 kg/h Temperature: 322 K (48.85’C) Pressure: ?

Number of Stages = 32 (reboiler + sump) Number of Trays = 30

Feed at Stage 16 Reflux ratio = 2

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Overview of case study

C3 0.4 wt%

iC4 0.6 wt%

C3 0.98 wt%

iC4 0.02 wt%

C3 0.01 wt%

iC4 0.99 wt%

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How to begin?

Develop the distillation column system

Specify the C3 and iC4 in component selection

Choose a suitable property method

Define feed condition

Specify a reasonable operating condition

Run and check the results

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Develop the distillation column system

Pump (pressure changer library) Valve (pressure changer library)

Distillation column –

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Connect all the blocks

Select material stream to insert stream in the flowsheet

Connect all the red input and

output (primary stream)

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A complete distillation system

Click the

V1

V12

V11

P11

P12

C1

FEED _DIST BOTM Rename all the blocks and streams

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Fill the specification menu

Select unit measurement Note:

You can also use your own set of unit by using Unit-Sets option under the Setup Menu

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Edit Report Options

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Specify the component

Use the Find button to search the components

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Select the property method

Select Chao-Seader property method

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How to calculate the pressure in FEED?

• Cooling water at condenser is expected to be at 305 K (31.85’C)

• Heuristic temperature different for heat transfer in condenser is 20 K • Therefore, the reflux drum temperature is ~ 325 K

• Vapor pressure for C3 at 325 K is ~ 14 atm • Assume the pressure drop in the V1 is 5 atm • So, FEED stream pressure > 19 atm

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Distillation column setup (Condenser)

Click the

button

Heuristic pressure drop in column =

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Pump 11 and Pump 12 Setup

Use pressure increase 6 atm for all pump

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V1 Setup

Use outlet pressure option

= 14.2 atm

Choose Liquid-Only

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V12 and V13 Setup

Use Pressure drop option

= 3 atm

Choose Liquid-Only

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Run the simulation

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The simulation run complete

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Check the results (Stream summary>>Streams)

The overall

result is still

not achieve

target 

Adjust to STREAMS Select the wanted streams

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Redesign: RR = 3

• Operating condition for RR is changed from 2 to 3 • Reinitialize the simulation and Run again

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Check the results (Stream summary>>Streams)

Separation target achieved

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Analysis Using Aspen Plus

• Binary Analysis – This tool will examine and plot the binary interaction between components.

• Azeotrope Analysis – To determine whether the mixture is azeotrope mixture or not

• Design Spec - This tool will help the user to achieve the production target by varying the specified operating condition.

• Sensitivity Tool – This tool will help the user to analysis the effect of specified operating condition over a certain region towards the

production target.

• Optimization – This tool will produce the optimized value for the operating condition in order to achieve the desired production target. This tool will automatically change the selected operating value to an optimized value after Run.

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ANALYSIS:

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Find Binary Analysis Menu

Access the Binary Analysis Menu under Tools Menu

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Select basis component

Binary Analysis Menu

Select type of analysis Select Unit and list/range for Pressure variation Property Method Click GO to start analysis

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Analysis Result

Txy Graph

Full

results

Use Plot Wizard to plot other type of graphs e.g. xy

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ANALYSIS:

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Azeotrope Analysis Menu

Select the menu

In this case, consider a feed of water and isopropane mixture to be analyzed. Here,

the property method selected is SRK

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Azeotrope Report

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The xy graph

azeotrope point

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ANALYSIS:

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Choose the Design-Spec Menu

Design Spec and Vary (below) menu

in the explorer

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Design Spec Tab Information

• Specification – define the target to be achieve in the simulation e.g. 99% composition in distillate stream

• Components – specify the target component

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Specify target value

Specification Tab

Select type of target

In this case, a mass purity target of 0.99% is desired

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Components Tab

Select the target component from

available components

Propone is selected as the target component

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Feed/Product Streams Tab

Specify the target stream from the available streams

Since the C3 product stream is at the top, thus the distillate stream is selected

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Vary Menu: To specify the varying variable for

Design-Spec

Vary Menu

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Specification Tab

Select the varying variable to be used. Must be a variable from the specified

operating conditions

Select a reasonable lower and upper

bound

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Run the simulation

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Check result in Vary Menu

Select the Results Tab

The final value of RR to achieve 99%C3 purity is 2.87

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ANALYSIS:

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Select: Sensitivity Study

Select the Sensitivity option from Model

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Sensitivity Study Tab Information

• Define: The user need to define the variable to be used as the production/simulation target.

• Vary: Choose the a variable from the specified operating conditions to be varied over selected region.

• Tabulated: Choose how the data will be tabulated. Usually, varied operating conditions vs. target value responses

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Insert new variable

Click New and enter a name for the target variable

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Select the target variable

In this case, we want

to specify the C3 mass

concentration in the

distillate stream as the

Target variable

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Select the Vary Variable

In this case, the Reflux

ratio (RR) is selected to be the Vary variable. The RR variable can be selected by specify C1 (the column) under Block-Var (Block variables).

Specify range: Lower and Upper boundary. Specify the number of point to be plotted Use search option

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Tabulate the variables

Click Fill variables button as Aspen will automatically

tabulated all the variables.

Click the

Check result

_{Choose Results. Make sure all the}

result is completed and converged (blue tick on the explorer)

Full results is available here under S-1 label Results summary for C3 composition by varying RR

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How to plot results in Aspen

Select the RR column in results summary

Click Plot from menu bar. Specify as X-axis.

Repeat the same procedure for C3 result. Finally, click the Display Plot under the same Plot menu

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The Sensitivity analysis results

The figure show the effects of varying the RR towards C3 composition. Based on the figure, the best RR value

to achieve the highest C3 purity would be around RR=4

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ANALYSIS:

OPTIMIZATION

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Select Optimization Menu

Optimization menu

Click New to create a new ID

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Define Tab

Click New to define a New optimization value

Enter the target variable name and Click OK

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Define the Target variable

Specify the Target variable

The optimization target variable is C3 mass purity in the distillate stream

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Objective & Constraints Tab

Select max or min

Specify the previously defined

variable name in the Define Tab

Constraint can also be specified in the Constraint Menu C3 composition is optimized to find the max purity

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Vary Tab

Specify number of varying variable

Select and specify the varying variable

Specify lower and upper boundary

RR is varied from 0.5 to 5 to find the max mass purity for C3 distillate product

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Run the simulation

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Check the results: Final C3 composition

Final value shows the max C3 distillate product composition can be achieved

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Check the results: New optimized RR value

The optimized RR value in the C1 Results Summary

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PART 4: FROM ASPEN PLUS

TO ASPEN DYNAMIC

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Using the same example:

A commonly used heuristic is to set these holdups to allow for 5 min of liquid holdup when the vessel is 50% full, based on the total liquid entering or leaving the vessel (Luyben, 2006)

• 100% full = 10 minutes of volume flowrate • From Hydraulic Tab:

Reflux drum volume = 0.00800586 m3_{/min (10min) = 0.0801 m}3

Sump volume = 0.00216335 m3_{/min(10min) = 0.0216 m}3

*Please refer to slide18 &19 for explanation on dynamic properties

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From Hydraulic Tab: Stage 1 => Reflux drum

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From Hydraulic Tab: Stage 32 => sump level i.e.

liquid entering reboiler from bottom tray

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Calculate the vessel geometry

Reflux drum: L = 0.9718m; D = 0.3239 m

Sump: L = 0.6279 m; D = 0.2093 m

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Entering the dynamic properties

Click this button to enter the dynamic properties

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Enter the dynamic properties in the column

configuration: Reflux drum and Sump Sizing

Enter the calculated Length and Diameter for

Reflux Drum and Sump

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Entering the properties for Hydraulic

calculation inside the column

Choose Rigorous Tray Calculation

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Additional Info

• Simple Tray: Using simple tray hydraulics equation relates the liquid flow rate from a tray to the amount of liquid on the tray. Here, the Francis weir equation for a single pass tray is used.

• Rigorous: The pressure drop across the tray is calculated by the same rigorous methods used for the steady-state simulation. The Francis weir equation is used to model the hydraulics based on the number of passes and tray geometry specified in the steady-state simulation.

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Tray Rating

Since we are using Rigorous Tray

Calculation, we need to specify the Tray Rating (so that Aspen Plus can perform the pressure drop calculation along the trays)

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Specify Tray Rating

Select Tray Rating menu under the C1

Click New and enter any ID number

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Specify Tray Rating

Enter the starting stage = 2 and End stage = 31 (In Aspen Plus; Stage1 = Condenser and Stage 32 =

Reboiler)

Enter the tray diameter, Tray type, Tray spacing and weir heights

Note: Default value for Tray spacing = 0.6069 m

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Pressure Drop profile

In order for the Aspen Plus to calculate and update the Pressure Drop profile inside the column, this

box must be tick

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Export to Dynamic (Flow Driven)

Click this icon for export our model into dynamic state (flow driven). A menu will pop up to rename and

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Additional Note:

Aspen provide two type of dynamic simulation i.e. flow driven and pressure driven. The icon for pressure driven simulation is just next to the flow driven in the menu. In the author experience, flow driven simulation is much simpler to develop compared to the pressure driven. Once the simulation is completed with no error, the simulation is ready to be export to the dynamic states in flow driven.

However, for pressure driven, all the pressure inside the streams in steady state model must be control by using pump or valve and its pressure must appropriate. There are also problem (depends) with irregular pressure drop inside the column and inconsistence pressure in feed and recycle stream. Use the Pressure checker icon to check the pressure within the SS model. Refer Process Simulation and Control Using Aspen by AK Jana.

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Find the saved file .dyn file

Click the saved file from previous menu. Generally, the file is saved

in the same folder as the SS simulation file

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Entering Aspen Dynamic (or Custom Modeler)

If all goes right, you should get this figure. Notice that in Aspen Dynamic, the basic controller is already implemented. These control loops are important to operate the column properly.

Click this set of icons to

run/pause/rewind (or restart) the simulation

Choose the state of simulation: Dynamic or Steady-state. Run Initialization at before starting dynamic simulation

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Additional Info:

• For distillation system, there are 3 major control loop that are essential to operate the column:-

1. Top / Condenser Pressure control loop –control energy balance 2. Reflux drum Level control loop –control mass balance (top)

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See simulation result

Run the simulation. Right click top product

stream. Select Forms and click TPFmPlot

During running the simulation, this panel will show the latest calculation step

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Results in real time form

This panel display the mass flowrate,

pressure and temperature for

the top product stream in real time. Use Zoom

Full option for clearer plot.

Although the graph is not steady, notice that the difference (in each parameter) is very small.

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#1 Select Tool in the top menu. Click New Form

#2 Name form and choose Plot

option

Specify custom parameter (e.g. Propane purity in top

product stream)

#3 The plot figure with no Y

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Specify specific parameter

#4 Right click top stream and choose Results in the Forms option

Specify custom parameter (e.g. Propane purity in top

product stream)

#5 From Results Table, drag the highlighted row (Propane purity) into the Y axis of the plot. The final figure should be like the one on the left. Run

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#6 We can now know the Propane composition in Distillate Stream in real time

Specify custom parameter (e.g. Propane purity in top

product stream)

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PART 5: ASPEN DYNAMIC

WITH MATLAB SIMULINK

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Getting Started with Aspen-Matlab

• Basically, AspenTech had made a collaboration with Mathworks to develop the AMS simulation system to connect Aspen Dynamic with Matlab Simulink

• However, there might be some compatibility issues regarding Aspen and Matlab version. Please refer to Aspen Help. Based on the author experiences:

 Aspen V7.2 compatible with Matlab 2009

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Use Aspen Dynamic Examples

• As an example, we are using the Simulink file in the Aspen Dynamic Examples

• Find the Aspen Dynamic instillation folder. Inside the folder, find the

Examples folder. Inside the example folder, click the Simulink folder;

C:\Program Files\AspenTech\Aspen Plus Dynamics V7.2\Examples

Click the MCH file (Simulink) as shown below:

Note: MCH is a simulation of extractive distillation of methylcyclohexane and toluene using phenol as an entrainer.

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The MCH simulation in Simulink

Notice that there are 4 control loops that are controlling the MCH column. Now, input s form the Aspen Dynamic

(via AMS Block) is supplied to the controller block. Then, the controller

action is computed in Simulink and returned back to the Aspen Dynamic

for further action.

AM-Simulation Block

A step input block act as the

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Configure AMSimulation Block

Click the AM-Simulation Block to open this menu

Use Browse to find the .dynf (Aspen Dynamic)

file

Input & Output represent the variables that being used in the AMS Block. Input refer to the input that is supplied to the Aspen Dynamic model (e.g. MV or DV). Output refer to the process variable (i.e. PV) that is produced from the model.

Click Connect to link with Aspen

Dynamic

MCH Model in Aspen Dynamic

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AMSimulation file

Before begin the Aspen-Matlab simulation, it is advised that we copy the AMSimulation file (m-file format) into the current

working folder (in Matlab) . The file is generally located inside the AMSystem folder in the Aspen installation folder.

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Running the simulation

Click

RUN

button in the Simulink to run the

simulation

Simulink

Scope

Aspen Dynamic

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How they work?

AM-Simulation

Aspen

Dynamic

Matlab

Simulink

Provide simulation data and result (present the PV) Compute and provide

controller action (decide the MV)

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What happen?

• Based on the previous figure (after running the simulation), Matlab Simulink had provided the initial Input (SS or initial value) for the Aspen Dynamic Model. Then, the input is processed (or calculated) by Aspen Dynamic to provide the current process variable (PV) values. The process variables is send back to Simulink environment via AMS Output.

• Based on the output that we had selected (in the AMS box), the output will provide the latest PV for Simulink Matlab to calculate its next MV. The new MV is then supplied back to the Aspen Dynamic via AMS Input and so on.

• One of the ways to set the initial value for the Aspen Dynamic is by using the unit delay box in Matlab Simulink.

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Simulation Time

• In the author opinion, it is important to synchronize the Aspen Dynamic and Matlab Simulink simulation time.

• This can be done via RUN (in the menu bar) >> Run Option or select F9.

Adjust the time units to match both simulation

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Simulation model vs. predictive model

u(k)

Simulation Model _{(Aspen Dynamic)}

y(k)

u(k)

Predictive

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Special Thanks

• Assoc. Prof Dr. Norashid Bin Aziz (USM) • Assoc. Prof Dr. Zainal Bin Ahmad (USM) • Imam Mujahidin Iqbal, Msc (USM)

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Aspen Plus & Dynamic Workshop (Step by Step)

Aspen Plus & Aspen

Dynamic Workshop

Driven by Innovation

Presentation Outline

Presentation Outline

PART 1:

Introduction to AspenONE

General Simulation Problem

Flowsheet Simulation

Approaches to Flowsheet Simulation

Sequential-Modular

Approach

Equation Oriented

Approach

Advantage of Simulation

Good Flowsheeting Practice

What is Aspen Plus?

Aspen Plus Inputs

Aspen Plus

Process

Simulation

Model Inputs

What Aspen Plus can do?

Aspen Plus Extension: Aspen Dynamic

Adding Dynamic Data

Steady state vs. Dynamic dilemma

Steady state

• All properties are steady

(not changing over time).

• Can be used to study

different steady state

conditions for a specific

range of properties either at

operating conditions or

off-design conditions.

Dynamic

• Ability to model the time

varying behaviour of a

system (changing over time)

• Used to analyse the

dynamic behaviour

(response) of complex

systems.

Advantages of Steady State Simulation

Advantages of Dynamic Simulation

Application for SS and Dynamic Simulation

How Aspen can help me with my research?

PART 2:

BEFORE STARTING WITH

ASPEN PLUS

Process “know how”

Process Analysis

Aspen Property Method

Case Study - Acetone Recovery

Ideal vs. Non-Ideal Behavior

Common Property Methods

Choosing a Property Method - Review

PART 3:

GETTING STARTED WITH

ASPEN PLUS

Case Study

Overview of case study

C3 0.4 wt%

iC4 0.6 wt%

C3 0.98 wt%

iC4 0.02 wt%

C3 0.01 wt%

iC4 0.99 wt%

How to begin?

Develop the distillation column system

Connect all the blocks

Connect all the red input and

output (primary stream)

A complete distillation system

NEXT

V1

V12

V11

P11